1. Technical Field
The present invention relates to a fixing device, an image forming apparatus, a fixing method and an image forming method. More specifically, it relates to a fixing device included in a copy machine, a printer or the like with an electrophotographic method, and the like.
2. Related Art
Conventionally, in an image forming apparatus with an electrophotographic method, a toner image formed on a recording medium such as a paper sheet is fixed on the recording medium by using a heat and pressure fixing method, in general. As the heat and pressure fixing method, a method (roll nip method) in which an unfixed toner image is heated and pressed at a nip portion formed between a fixing roll incorporating a heater and a pressure roll to be fixed on the recording medium, and a method (belt nip method) in which a pressure pad presses a recording medium against the fixing roll from an inner side of an endless belt to form a nip portion are exemplified.
In the heat and pressure fixing method, a high quality image without unevenness is considered to be obtained by uniformly maintaining surface temperatures of the fixing roll and the pressure roll. Thus, there has been developed a technique for uniformly maintaining the surface temperatures of the fixing roll and the like even when, for example, the fixing roll and the pressure roll remains in a state where they are heated and pressed without rotation (a stand-by state or a stand-by mode).